The present invention relates to a laser apparatus, and more particular to a discharge electrodes structure in a laser apparatus and a laser apparatus provided with the discharge electrodes.
Conventionally, there has been known a laser apparatus which excites a laser medium in accordance with a discharge so as to oscillate a laser beam, and the laser apparatus is, for example, described in U.S. Pat. No. 4,959,840. FIG. 24 shows a cross section near discharge electrodes of an excimer laser apparatus disclosed in the publication, and a description will be given of a conventional art on the basis of FIG. 24.
In FIG. 24, an excimer laser apparatus 101 is provided with a laser chamber 102 for sealing a laser medium such as a laser gas or the like. the laser chamber 1-2 can be freely divided into an upper chamber 102A and a lower chamber 102B. A pair of discharge electrodes 105A and 105B constituted by an anode 105A and a cathode 105B for generating a discharge so as to excite a laser gas and oscillate a laser beam are arranged in an inner portion of the laser chamber 102 in an opposing manner.
The anode 105A is fixed to an anode base 106 made of a conductive body by a bolt 160, and the anode base 106 is gripped between the upper chamber 102A and the lower chamber 102B. Accordingly, the anode 105A is in the same electric potential as that of the laser chamber 102 (is grounded).
Further, the cathode 105B is fixed to a cathode supporting member 108 made of an insulative body by a high voltage current supply rod 112, and is electrically insulated from the laser chamber 102 by insulative members 109 and 110 made of an insulative body such as a ceramic or the like. A high voltage current for being discharged to the cathode 105B is supplied by the high voltage current supply rod 112.
However, the conventional art disclosed in U.S. Pat. No. 4,959,840 has the following problems.
That is, during the discharge operation, the opposing portions of the discharge electrodes 105A and 105B are gradually abraded and consumed. Accordingly, an interval between the discharge electrodes 105A and 105B is increased, and a shape of the discharge electrodes 105A and 105B is changed. Therefore, since the discharge operation becomes unstable so as to prevent a power of the laser beam from changing, it is necessary to regularly replace the discharge electrodes 105A and 105B. In particular, since the anode 105A is greatly consumed in comparison with the cathode 105B, it is necessary to frequently replace the anode 105A.
However, in accordance with the conventional art, the cathode 105B is fixed to the upper chamber 102A and the anode 105A is gripped between the upper chamber 102A and the lower chamber 102B. Accordingly, in order to replace the discharge electrodes 105A and 105B, it is necessary to separate the upper chamber 102A from the lower chamber 102B, replace the discharge electrodes 105A and 105B, thereafter again assemble the upper chamber 102A and the lower chamber 102B, so that a lot of labor and time are required. Further, at this time, in order to stabilize the discharge operation, it is necessary to accurately adjust a distance between the anode 105A and the cathode 105B in a state of assembling the anode 105A and the cathode 105B in the laser chamber 102, and this adjustment required a lot of labor and time.
Further, by separating the upper chamber 102A and the lower chamber 102B, an inner wall of the laser chamber 102 and parts such as a blower (not shown) or the like arranged in an inner portion of the laser chamber 102 are exposed to an air. As a result, a moisture content and an impurity contained in the air are attached to the inner wall of the laser chamber 102, the blower or the like so as to soil the laser gas, so that a power of the laser beam is reduced. In order to prevent the power from being reduced, there is required a passivation corresponding to an operation of removing the attached moisture content and impurity. Accordingly, it is necessary to stop the excimer laser apparatus 1 for a long time at every replacement of the discharge electrodes 105A and 105B, so that the machine availability is reduced.
The present invention is made by solving the problems in the conventional art mentioned above, and an object of the present invention is to provide a discharge electrodes structure which can be easily replaced and adjustable a distance between the discharge electrodes, and a laser apparatus employing the discharge electrodes.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a laser apparatus provided with a discharge electrodes structure comprising:
a pair of anode and cathode provided within a laser chamber for sealing a laser medium in an opposing manner, generating a discharge so as to excite the laser medium and oscillating a laser beam;
a conductive anode base holding the anode;
an insulative cathode base placed so as to close an opening portion provided in the laser chamber and holding the cathode; and
a return plate suspending the anode base from the cathode base so as to supply a current to the anode.
In accordance with the structure mentioned above, since the anode is suspended from the cathode by the return plate, it is possible to integrally attach and detach the anode and the cathode to and from the laser chamber at a time of replacing any one of the anode and the cathode. Accordingly, when the structure is made, for example, such that the anode and the cathode are assembled in an external portion of the laser chamber so as to unite and the unit is replaced, it is possible to save labor and time for assembly in comparison with the case of independently assembling the anode and the cathode within the laser chamber.
Further, the laser apparatus provided with the discharge electrodes structure may further comprise an anode support bar for connecting the cathode base to the anode base so as to suspend the anode from the cathode base.
In accordance with the structure mentioned above, since the anode is suspended by not only the return plate but also the anode support bar, it is possible to weaken a strength of the return plate so as to make a thickness and a width of the return plate thin. Accordingly, the return plate does not disturb a flow of the laser medium flowing between the anode and the cathode, so that a flow speed becomes fast and the discharge operation is stably performed.
In addition, for example, when the structure is made such that the anode support bar is provided with a mechanism for positioning the anode and the cathode with respect to each other, it is easy to assemble the anode and the cathode.
Further, the laser apparatus provided with the discharge electrodes structure may be structured such that the anode base is freely separated into an upper anode base for holding the anode and a lower anode base connected to the return plate.
In accordance with the structure mentioned above, since the anode and the lower anode base connected to the return plate are separated, it is unnecessary to take out the return plate at a time of taking out the anode from the laser chamber. Accordingly, it is possible to save labor and time for replacing a battery.
Further, there is provided a laser apparatus provided with a discharge electrodes structure comprising:
a pair of anode and cathode provided within a laser chamber for sealing a laser medium in an opposing manner, generating a discharge so as to excite the laser medium and oscillating a laser beam;
a conductive anode base placed so as to close an opening portion provided in the laser chamber and holding the anode;
an insulative cathode base holding the cathode; and
a return plate connecting the anode base to the cathode base and suspending the cathode base from the anode base so as to supply a current to the anode.
In accordance with the structure mentioned above, even in the laser apparatus structured, for example, such that the anode is arranged in the upper portion and the cathode is arranged in the lower portion, it is possible to integrally take the anode and the cathode out of the laser chamber. Accordingly, it is possible to save labor and time for replacing the electrodes.
Further, the laser apparatus provided with the discharge electrodes structure may be structured such that the anode is freely attached and detached with respect to the anode base so as to take the anode out of the laser chamber.
At a time of discharge, the anode is earlier consumed than the cathode. In accordance with the present structure, since it is possible to take the anode which is required to be frequently replaced out of the laser chamber in such a manner as to be independent from the cathode so as to be replaced, it is possible to save labor and time for replacing the battery.